Small Initial Size Research Articles

Unexpected insularity effects in invasive plant mating systems: the case of Carpobrotus (Aizoaceae) taxa in the Mediterranean Basin

Although biological invasions are currently recognized as being especially severe on islands, little attention has been given to detecting parameters influencing this pattern. This study tested the common perceptions that uniparental reproductive modes are associated with invasive and/or island plant populations due to a lack of pollinator vectors and/or small initial population sizes, and that pollinator services and biparental seed production modes will subsequently be associated with adjacent mainland sites. Using controlled pollination and germination experiments on invasive Carpobrotus edulis and C. aff. acinaciformis populations in both island and mainland habitats in south-east France, we found no evidence to support these hypotheses. All significant mean differences found between locations for reproductive indices describing uniparental reproductive modes were significantly smaller in island populations. In contrast, seedling sizes issuing from manual outcrossing and manual hybridization experiments, regardless of taxon, as well as C. aff. acinaciformis hybridization indices, were larger in island populations. The presence of significant, though limited, pollinator service was detected for all populations, and stressed the importance of such mutualisms. We suggest that invasive plant reproductive traits could be highly contextual, and that islands may have a potential role in the acceleration of the invasion process through the production of highly variable populations. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 65‐79. ADDITIONAL KEYWORDS: agamospermy ‐ hybrid vigour ‐ inbreeding depression ‐ island invasion ‐ pollinator limitation ‐ self fertilization.

Surgery of «low» rectal cancer — prospects of modern oncoproctology

Use of endoscopic ultrasonography in diagnostics of rectal low-ampullar malignant neoplasms has permitted to the authors to define the list of intersphincteric resection indications consisted in total mesorectumectomy and rectal and interior sphincter resection. The method of spheroidal reservoir formation with artificial unstriped muscular sphincter-cuff has been developed for the prophylaxis of anal incontinence and multimoment emptying after intersphincter resection with the colon bringing down. 14 patients have been operated with survey time up to 3,5 years. According to the data of clinical investigations the spheroidal reservoir form with small initial size and with the ability to extensibility as well as autonomous obturator function of striped muscular sphincter have become the basic conditions for the restoration of continence act and stool frequency in far period after intersphincter resection.

Seasonal phenotypes of Daphnia: post-diapause and directly developing offspring

Life-history and physiology of post-diapause and directly developing offspring in Daphnia were compared to determine differences in life-history pattern between offspring origins, identify the basic traits effecting pattern distinction, assess the consequencies of differing life-history for relative fitness, and qualify this seasonal phenomenon. Although the size of ex-ephippial hatchlings was positively correlated with maternal size, ephippia produced by differently sized females of D. magna yielded neonates which body size and it’s variation were similar to those for the first-clutch parthenogenetic neonates produced under high food conditions. Otherwise, post-diapause neonates of D. pulex were larger than first-clutch parthenogenetic neonates and varied in size close to that for neonates from the later clutches. Ex-ephippial offspring showed elevated metabolic activity. Under rich food, they grew faster during juvenile development and were larger at maturation than parthenogenetic females. Post-diapause offspring of D. magna showed higher juvenile growth rates also at limited food availability. Female origins during early maturity differed in resource allocation strategy. A greater allocation to progeny in offspring exiting diapause, however, resulted in increased progeny numbers and higher relative fitness only under rich food environments. Whereas, parthenogenetic females of D. magna exhibited a trend for higher fitness across limited food concentrations. For D. pulex, variability of fitness across differing nutritional environments was lower in directly developing females than that for ex-ephippial offspring. Higher metabolic activity in combination with small initial size resulted in lower resistance to starvation of post-diapause offspring of D. magna. Descendants of female origins in this species showed similar fitness. We conclude that although some traits of ex-ephippial offspring in comparison to parthenogenetic ones may differ across Daphnia species, the life-history strategy of post-diapause females in Daphnia is the same. Ex-ephippial females are adapted to predictable optimal conditions, whereas parthenogenetic females are adapted to unpredictably varying environment. Daphnia have evolved two alternative seasonal phenotypes matching environmental conditions in which they occur, and perform in accordance with predictions of seasonal polyphenism. Due to higher metabolic activity, which must lead to increased resource acquisition and probably is associated to larger allocation to progeny, post-diapause females are superior to directly developing offspring under high food conditions, which are expected during early season, but inferior under limiting food environments, which frequently occur later in the season. In seasonal climate, the adjustment of resource acquisition with respect to resource availability may be a general evolutionary trend for multivoltine organisms resulting in a seasonal polyphenism.

The construction of confidence intervals for frequency analysis using resampling techniques

Abstract. Resampling techniques such as the Bootstrap and the Jack-knife are generic methods for the estimation of uncertainties in statistics. When applied in frequency analysis, resampling techniques can provide estimates of the uncertainties in both distribution parameters and quantile estimates in circumstances in which confidence limits cannot be obtained theoretically. Test experiments using two different parameter estimation methods on two types of distributions with different initial sample sizes and numbers of resamples has confirmed the utility of such methods. However, care is necessary in evaluating the skewness of the resampled quantiles, especially with small initial sample sizes. Keywords: Bootstrap, Jack-knife, frequency analysis, maximum likelihood method, maximum product of spacings method

Microstructure and rheology of an AA2024 aluminium alloy in the semi-solid state, and mechanical properties of a back-extruded part

The effect of deformation mode (rolling and extrusion) on the efficiency of microstructural conditioning and microstructural evolution of a semi-solid AA2024 alloy was studied by optical microscopy and X-ray diffraction. Results show that although the extruded sample produced a very small initial particle size, its initial growth rate is faster, a behaviour ascribed to its accentuated texture. However after 600 s in the semi-solid state, rolled and extruded samples exhibit the same degree of texture and very similar growth rates, whose rate-controlling mechanism was found to be particle coalescence. A separate study on rolled material showed that the higher the deformation ratio, the smaller the initial particle size and that a thickness reduction of 30% is sufficient to obtain a fine distribution of Al-α particles. Simple compression tests showed that the rheological behaviour of the AA2024 alloy is adequately described by the power law. Moreover, the alloy exhibited solid-like behaviour before fracture of the solid skeleton and pseudoplastic behaviour after that. Finally, a sound and crack-free demonstration part was produced by back-extrusion. The item displayed both macro- and microsegregation but solution heat treatment was reasonably effective to equalise solute concentration. Tensile properties were equivalent to those of conventionally forged material although local differences throughout the part were observed. Results have important implications on the production of suitable semi-solid microstructures and on the mechanical behaviour of thixoformed parts.

Life-history models of extinction: a test with island spiders.

This study analyzes extinction patterns for two species of orb spiders monitored annually on 77 islands over a continuous 20-yr period. One species, Argiope argentata, has large populations sometimes crashing quickly to extinction and a much weaker relation of extinction likelihood to population size than does the other species, Metepeira datona. Demographic models were built for both species and matched against observations. Differences between the species in life-history traits-estimated with measurements from the field-together with incorporation of demographic stochasticity, a population ceiling, and environmental stochasticity, were necessary to fit the observed extinction curves. As predicted from life-history patterns, long-term population growth rates (and hence predicted extinction probabilities) are relatively very sensitive to values of juvenile survivorship. Models are also sensitive to variation in the population ceiling and environmental noise, which tend to act in a complementary manner. A simple model with no age structure was able to fit the data on large initial population sizes but not on small initial population sizes, showing that life cycle characteristics interact with the various sources of stochasticity and hence have to be taken into account to produce a precise model of the extinction process.

Bubble size in coalescence dominant regime of turbulent air–water flow through horizontal pipes

An experimental study was performed in a 25.4 mm ID pipeline to evaluate the development of the bubble size distribution in the horizontal flow of an air–water system. As the air stream enters into the flowing water stream through a T-injector, it breaks into bubbles with a log-normal size distribution. Because of the small water velocity (1–3 m/s) and small initial bubble size, coalescence, not breakage, plays the dominant role in the present study. The effects of average water velocity, air volume fraction and air injector diameter on the initial bubble size distribution and its evolution along the length of the pipe in the coalescence dominant regime are investigated. At larger water velocities, the log-normal bubble size distributions are also maintained downstream of the injector. At smaller velocities, the distributions deviate slightly from the log-normal pattern. For all distributions, the value of the ratio d 99.8/ d 32 is about 2.2 and is fairly independent of average water velocity, pipe length, air volume fraction and air injector diameter. It is found that at large velocities of water, the prediction of d max through Levich’s breakup theory agrees well with the experimental d 99.8 values for air volume fraction up to 0.003.

Gouy phase shift of single-cycle picosecond acoustic pulses

Ultrafast laser pulses are used to generate single-cycle picosecond acoustic pulses in thin metal films on silicon. For small initial excitation spot sizes, propagation of the acoustic pulses across a 485-μm Si crystal leads to significant diffraction effects. The temporal reshaping of the acoustic wave form due to diffraction is investigated, and we demonstrate that the acoustic far field can be reached.

The Effect of Initial Grain Size on Transition from Discontinuous to Continuous Recrystallization in a Highly Cold Rolled Al-Fe-Mn Alloy

The deformation microstructures and the recrystallization behaviour of a highly deformed Al-Fe-Mn alloy has been investigated using high resolution EBSD. Of particular interest have been the effects of the initial grain size and the strain on the nature of the recrystallization process. The results show that conventional discontinuous recrystallization takes place for large initial grain sizes and low to moderate strains. However, small initial grain sizes and large strains promote a transition to continuous recystallization and a resultant micron-grained product.

Produced water from polymer flooding process in crude oil extraction: characterization and treatment by a novel crossflow oil–water separator

Produced water from polymer flooding was much more difficult to be treated than that from water flooding in many oilfields. The simulated experimental results showed that the small initial sizes of oil droplets were the main reason that caused the difficulty in treating the produced water from the polymer flooding process. Polymer hydrolyzed polyacrylamide (HPAM) increased oil–water separation when its concentration was less than 790 mg l −1 . The flocculating effect by the polymer was found to play a dominant role at low HPAM concentration, even though it increased the wastewater viscosity and water film strength. Enhancing the coalescence of oil droplets and shortening rising time of oil droplets were the critical factors affecting the treatment of produced water. A novel crossflow oil–water separator with coalescence and separation sections was exploited. The coalescence section accelerated the coalescence of the small oil droplets and the separation section shortened the rising time of oil droplets. The in situ experiments showed that the separator successfully treated the produced water from the polymer flooding. When the polymer concentration was below 410 mg l −1 , the quality of the treated water after the separator can meet the water requirement for the subsequent filtration processes.

Abnormal grain growth in bulk Cu—The dependence on initial grain size and annealing temperature

The dependence of abnormal grain growth (AGG), also termed secondary recrystallization, on annealing temperature in the range between 600 °C and 1050 °C has been observed in pure bulk Cu specimens compressed to various levels between 5 and 75 pct. There is no grain texture after annealing. The average grain size after primary recrystallization, which represents the initial grain size for secondary recrystallization during further annealing, decreases with increasing deformation and is nearly independent of the annealing temperature, in agreement with previous observations. The incubation time for AGG decreases and the number density of abnormally large grains increases with increasing deformation (hence, a decreasing initial grain size) and increasing annealing temperature. At low temperatures, most of the grain boundaries are faceted, with some facet planes probably of singular structures corresponding to cusps in the polar plots of the grain-boundary energy vs the grain-boundary normal. With increasing temperature, the grain boundaries become defaceted and, hence, atomically rough. The observed grain-growth behavior appears to be qualitatively consistent with the movement of faceted grain boundaries by two-dimensional nucleation of boundary steps. The temperature dependence appears to be consistent with roughening of grain boundaries. Before the onset of AGG, stagnant growth of the grains occurs at low rates, probably limited by slow two-dimensional nucleation of boundary steps, and, at low deformations and low annealing temperatures, the stagnant growth persists for 100 hours. The specimens with relatively small initial grain sizes (because of high deformation) show double AGG when annealed at high temperatures.

Study analyses antioxidant masterbatch preparation for linear polyethylene

This study focuses on the impact of initial particle size on the tabletability and the deformation behaviour (i.e. plasticity) of granules produced by twin-screw melt granulation (TSMG). As model substances, three different grades of anhydrous dicalcium phosphate (aDCP) were melt-granulated with polyethylene glycol 6000 (PEG) using a twin-screw granulator. Compaction performance of the granules and the corresponding physical mixtures (PM) was evaluated by in-die and out-of-die compaction analysis. A major impact on granules deformation behaviour was found for the relation of the specific surface area of the filler material to the binder content. A relative yield pressure (YP) was introduced to describe the enhancement in plastic deformation behaviour, defined as the plasticity performance factor (PPF). Furthermore, a modified Kawakita model was used to describe the granulation efficiency, compared to a calculated physical mixture model. Granules under investigation showed an increased plastic deformation, enhanced tabletability and reduced elastic recovery (ER). The binder was shown to be finely distributed and to fill the voids between the aDCP particles (image analysis of the carbon energy dispersive X-ray maps). A small initial particle size of filler material (DI-CAFOS® A7 and A12) was more efficient than a larger particle size (DI-CAFOS® A60). A very low particle size (DI-CAFOS® A7) required the addition of 1% (w/w) colloidal silicon dioxide to enable feeding of the material into the granulator. Moreover, due to the larger surface area of these particles, a higher amount of binder was necessary to achieve a low PPF and a high tensile strength (TS).

ACTIVE RECOVERY BETWEEN HIGH-INTENSITY EXERCISE BOUTS IMPROVES PERFORMANCE IN HOCKEY PLAYERS

Background Active recovery (AR) compared to passive recovery (PR) between high-intensity exercise bouts increases total work achieved and promotes lactate clearance in hockey players. Previous studies applied AR via submaximal exercise sessions to reduce post-event fatigue. However, no study to date has applied AR between repeated supramaximal exercise bouts. Preliminary Data 6 sedentary subjects (4 male, 2 female) and 5 athletic subjects (3 male, 2 female) were tested to examine the effect of AR vs PR between consecutive 30-second supramaximal exercise bouts. Total work (joules) was higher in the athletic group than in the sedentary group (2871 vs. 1029; p < .02). Additionally, the data demonstrate a significant treatment effect of AR vs. PR (2127 vs. 1046; p < .02) as well as a significant interaction effect (p < .02). Thus AR, between supramaximal exercise bouts improves overall performance in normal subjects and athletes. Hypothesis AR between repetitive bouts of supramaximal activity in ice hockey players will result in greater performance as defined by total work achieved, and lactate clearance. Methods 3 amateur hockey players (3 male, mean age 26 ± 3 years, mean weight 83.5 ± 11.2 kg, mean VO2 max 45 ± 2.8 ml/O2/min) were tested. Each subject underwent three days of testing. Day 1 consisted of a baseline 30-second Wingate Power Test (WPT) on a Monark 818-E ergometer and baseline VO2 max testing on a Sensormedics electronically braked ergometer. On days 2 and 3, subjects were required to perform consecutive WPTs with a randomly-assigned 4-minute recovery period (AR at 28% of peak power, or PR) in between, until a 30% reduction in power occurred. Capillary lactate was taken when subjects reached a 30% reduction in power and every 5 minutes for 30 minutes after testing was completed. Results Means for total work achieved (joules) were 8646 with AR and 7151 with R, a significant difference (p < .021). In addition, capillary lactate levels (mmol) at the time of a 30% power reduction were 12.5 with AR, as compared to 15.8 with PR (p < .02). Conclusion This study is the first to document the dramatic beneficial effect of AR in between high-intensity exercise bouts in hockey players. Since the prevailing standard of recovery in ice hockey is PR, these results have potentially important implications in the recovery period between exercise bouts during a hockey game. Despite a small initial sample size, there is a significant effect of AR on performance, and currently further study is underway. The data also suggests that AR may be extremely valuable in sports where repetitive short bursts of high-intensity activity are required or in sports where muscle lactate accumulation may hinder performance. Supported by ACSM Reebok Grant for Human Performance and Injury Prevention 2000.

Memory system behavior of Java programs

This paper studies the memory system behavior of Java programs by analyzing memory reference traces of several SPECjvm98 applications running with a Just-In-Time (JIT) compiler. Trace information is collected by an exception-based tracing tool called JTRACE, without any instrumentation to the Java programs or the JIT compiler. First, we find that the overall cache miss ratio is increased due to garbage collection, which suffers from higher cache misses compared to the application. We also note that going beyond 2-way cache associativity improves the cache miss ratio marginally. Second, we observe that Java programs generate a substantial amount of short-lived objects. However, the size of frequently-referenced long-lived objects is more important to the cache performance, because it tends to determine the application's working set size. Finally, we note that the default heap configuration which starts from a small initial heap size is very inefficient since it invokes a garbage collector frequently. Although the direct costs of garbage collection decrease as we increase the available heap size, there exists an optimal heap size which minimizes the total execution time due to the interaction with the virtual memory performance.

The effect of pre-strain and strain-path changes on ductile fracture: experiment and computational modeling

Based on experiments and computational modeling, this study examines the failure behavior of structural steel, HY-100, which has been pre-strained at a high stress triaxiality and subsequently failed at a lower stress triaxiality. Both tensile tests of circumferentially notched specimens and the associated fractography show that even a small pre-strain at high stress triaxiality promotes an extension of the low ductility, ‘void-sheet’ mode of failure to lower stress triaxialities. Thus, there is a decrease in the failure strain compared to that if the material is deformed only at the lower stress triaxiality. These results imply that the pre-strain damage nucleates elongated voids whose growth is critical to the development of void-sheet failure. Micro-mechanical modeling using finite element analysis confirms that localization of plastic flow should occur between elongated ‘hole shaped voids’, despite their rather small initial cross-section size (2.5 μm) and comparatively large spacing (70 μm). Furthermore, employing a local failure criterion, the computational analysis predicts failure strains which are in good agreement with those observed after the pre-strain and strain-path change.

Population Extinction and Quasi-stationary Behavior in Stochastic Density-dependent Structured Models

Density-independent and density-dependent, stochastic and deterministic, discrete-time, structured models are formulated, analysed and numerically simulated. A special case of the deterministic, density-independent, structured model is the well-known Leslie age-structured model. The stochastic, density-independent model is a multitype branching process. A review of linear, density-independent models is given first, then nonlinear, density-dependent models are discussed. In the linear, density-independent structured models, transitions between states are independent of time and state. Population extinction is determined by the dominant eigenvalue λ of the transition matrix. If λ≤ 1, then extinction occurs with probability one in the stochastic and deterministic models. However, ifλ> 1, then the deterministic model has exponential growth, but in the stochastic model there is a positive probability of extinction which depends on the fixed point of the system of probability generating functions. The linear, density-independent, stochastic model is generalized to a nonlinear, density-dependent one. The dependence on state is in terms of a weighted total population size. It is shown for small initial population sizes that the density-dependent, stochastic model can be approximated by the density-independent, stochastic model and thus, the extinction behavior exhibited by the linear model occurs in the nonlinear model. In the deterministic models there is a unique stable equilibrium. Given the population does not go extinct, it is shown that the stochastic model has a quasi-stationary distribution with mean close to the stable equilibrium, provided the population size is sufficiently large. For small values of the population size, complete extinction can be observed in the simulations. However, the persistence time increases rapidly with the population size.

Measurements of Flow Speeds in the Corona Between 2 and 30R☉

Time-lapse sequences of white-light images, obtained during sunspot minimum conditions in 1996 by the Large Angle Spectrometric Coronagraph on the Solar and Heliospheric Observatory, give the impression of a continuous outflow of material in the streamer belt, as if we were observing Thomson scattering from inhomogeneities in the solar wind. Pursuing this idea, we have tracked the birth and outflow of 50-100 of the most prominent moving coronal features and find that: 1. They originate about 3-4 R☉ from Sun center as radially elongated structures above the cusps of helmet streamers. Their initial sizes are about 1 R☉ in the radial direction and 0.1 R☉ in the transverse direction. 2. They move radially outward, maintaining constant angular spans and increasing their lengths in rough accord with their speeds, which typically double from 150 km s-1 near 5 R☉ to 300 km s-1 near 25 R☉. 3. Their individual speed profiles v(r) cluster around a nearly parabolic path characterized by a constant acceleration of about 4 m s-2 through most of the 30 R☉ field of view. This profile is consistent with an isothermal solar wind expansion at a temperature of about 1.1 MK and a sonic point near 5 R☉. Based on their relatively small initial sizes, low intensities, radial motions, slow but increasing speeds, and location in the streamer belt, we conclude that these moving features are passively tracing the outflow of the slow solar wind.

Relationships between recruitment and postrecruitment processes in lagoonal populations of two coral reef fishes

Pomacentrus amboinensis Bleeker and Dascyllus aruanus (L.) exhibit similar large scale patterns in recruitment to One Tree lagoon, southern Great Barrier Reef. They recruit in greatest numbers near the windward perimeter compared with the centre of the lagoon, and at the perimeter, recruit preferentially to deeper sites (4–8 m depth). This pattern was observed in recruitment to standard coral heads of Pocillopora damicornis (L.), a preferred substratum transplanted to a range of locations and depths. As substratum was held constant, spatial variation in recruitment was not determined by the availability of suitable habitat. Patterns in growth and mortality of the two fish species were monitored for juveniles transplanted to another set of standard coral heads, in order to determine whether post-recruitment processes would reinforce or disrupt patterns established at the time of recruitment. The two species exhibited contrasting patterns. Pomacentrus amboinensis exhibited faster growth and better survivorship at deeper sites, regardless of the location in the lagoon, reinforcing the initial pattern. Dascyllus aruanus exhibited faster growth at perimeter sites and significantly better survivorship at central sites, patterns that would tend to disrupt the initial pattern. Within locations, individuals exhibiting slower growth rates ( Pomacentrus amboinensis) or smaller initial size ( Dascyllus aruanus) had reduced life expectancy. The results suggest that location selection by settlers of Pomacentrus amboinensis results in improved growth and/or survival. This was not the case for Dascyllus aruanus, which is probably more influenced by the presence of conspecifics. However, even for Pomacentrus amboinensis, large-scale patterns probably reflect constraints on habitat selection. Recruitment in Pomacentrus amboinensis was consistently lower to sites immediately down current of other reefs, regardless of their position. I suggest that the absence of recruits of both species to central sites indicates that this region is a recruitment-shadow. Juveniles settle in preferred habitat at the first opportunity after entering the lagoon, leaving much of the preferred habitat in the centre of the lagoon unoccupied. Patterns are initially recruitment-determined, but either reinforcement or disruption mean that the numerical abundance of adults cannot be predicted on the basis of recruitment data alone.

Apolipoprotein E4 genotype and gallbladder motility influence speed of gallstone clearance and risk of recurrence after extracorporeal shock-wave lithotripsy.

Extracorporeal shock-wave lithotripsy (ESWL) is an effective treatment in selected gallstone patients, but stone recurrence is a major drawback. Factors potentially influencing gallstone clearance and recurrence were studied in 84 patients in whom stone dissolution was diagnosed after ESWL plus bile salt therapy for initial solitary (n = 55) or multiple (n = 29) radiolucent stones. Apolipoprotein E (apoE) genotyping and gallbladder motility (sonography) were studied in a representative subgroup of patients (n = 50). The median follow-up after ESWL was 36 months (range, 4.5-67 months). Gallstone clearance was achieved after 8.7 months (range, 0.2-30 months). Independent factors significantly enhancing gallstone clearance were the presence of E4 allele; small initial gallstone size and number; effectiveness of fragmentation; and good gallbladder emptying (P = .002). Gallstone recurrence was seen in 30 patients after 18.6 months (range, 1.0-50 months). Cumulative gallstone recurrence rate (life-table analysis) was 15% within 1 year, increasing to 60% within 5.5 years. Although the probability of gallstone recurrence tended to be smaller in patients with initial solitary stones than in those with multiple stones during early follow-up, differences disappeared after long-term follow-up. Effective gallbladder emptying (residual volume < or = 6 mL) and apolipoprotein E4 (apoE4) independently influenced gallstone recurrence. Recurrence rate was higher (log rank test, P = .037) in those patients who were homozygous and heterozygous for the E4 allele compared with the individuals who were not expressing the apoE4 allele. Accordingly, there was an overrepresentation of the allele frequency for E4 in the group with gallstone recurrence (P =.03). Patients with small postprandial residual gallbladder volumes (</= 6 mL) had a lower probability of stone recurrence than those with large residual gallbladder volumes (log rank test, P = .0215). Biliary pain was more frequent with recurrence (55% vs. 13%, P = .001). The present study indicates that apoE4 genotype is associated with increased speed of gallstone clearance as well as a high risk of recurrence after ESWL. This finding points to a possible role for genetic factors in the pathogenesis of cholesterol gallstones. Effective gallbladder emptying is important for speed of clearance and prevention of recurrence. Patients with initial solitary stones have a decreased early- but not long-term gallstone recurrence rate.

Apolipoprotein E4 genotype and gallbladder motility influence speed of gallstone clearance and risk of recurrence after extracorporeal shock-wave lithotripsy

Extracorporeal shock-wave lithotripsy (ESWL) is an effective treatment in selected gallstone patients, but stone recurrence is a major drawback. Factors potentially influencing gallstone clearance and recurrence were studied in 84 patients in whom stone dissolution was diagnosed after ESWL plus bile salt therapy for initial solitary (n = 55) or multiple (n = 29) radiolucent stones. Apolipoprotein E (apoE) genotyping and gallbladder motility (sonography) were studied in a representative subgroup of patients (n = 50). The median follow-up after ESWL was 36 months (range, 4.5-67 months). Gallstone clearance was achieved after 8.7 months (range, 0.2-30 months). Independent factors significantly enhancing gallstone clearance were the presence of E4 allele; small initial gallstone size and number; effectiveness of fragmentation; and good gallbladder emptying (P = .002). Gallstone recurrence was seen in 30 patients after 18.6 months (range, 1.0-50 months). Cumulative gallstone recurrence rate (life-table analysis) was 15% within 1 year, increasing to 60% within 5.5 years. Although the probability of gallstone recurrence tended to be smaller in patients with initial solitary stones than in those with multiple stones during early follow-up, differences disappeared after long-term follow-up. Effective gallbladder emptying (residual volume < or = 6 mL) and apolipoprotein E4 (apoE4) independently influenced gallstone recurrence. Recurrence rate was higher (log rank test, P = .037) in those patients who were homozygous and heterozygous for the E4 allele compared with the individuals who were not expressing the apoE4 allele. Accordingly, there was an overrepresentation of the allele frequency for E4 in the group with gallstone recurrence (P =.03). Patients with small postprandial residual gallbladder volumes (≤ 6 mL) had a lower probability of stone recurrence than those with large residual gallbladder volumes (log rank test, P = .0215). Biliary pain was more frequent with recurrence (55% vs. 13%, P = .001). The present study indicates that apoE4 genotype is associated with increased speed of gallstone clearance as well as a high risk of recurrence after ESWL. This finding points to a possible role for genetic factors in the pathogenesis of cholesterol gallstones. Effective gallbladder emptying is important for speed of clearance and prevention of recurrence. Patients with initial solitary stones have a decreased early- but not long-term gallstone recurrence rate. (Hepatology 1996 Sep;24(3):580-7)